Process for dyeing leather

ABSTRACT

A process for dyeing leather, which comprises treating the leather with either A. AN AQUEOUS DYESTUFF SOLUTION THAT OPTIONALLY CONTAINS A WATER-MISCIBLE ORGANIC SOLVENT AND/OR A WETTING AGENT AND DISPERSING AGENT, B. A SOLUTION OF A DYESTUFF IN AN ORGANIC SOLVENT OR A MIXTURE OF ORGANIC SOLVENTS, OR C. AN AQUEOUS OR ORGANIC DISPERSION OF A DYESTUFF, EXPRESSING THE DYEING LIQUOR FROM THE DYED LEATHER, AND SUBSEQUENTLY DRYING THE LEATHER OR SUBJECTING THE LEATHER TO A FIXING PROCESS AND THEN DRYING IT.

United States Patent 1191 Bohny et a1.

n] 3,920,385 Nov. 18, 1975 PROCESS FOR DYEING LEATHER [75] Inventors:Fritz Bohny, Basel; Willi Egli,

Reinach; Max Schwank, Basel, all of Switzerland [73] Assignee:Ciba-Geigy AG, Basel, Switzerland [22] Filed:

[21] Appl. No.: 373,836

May 3, 1973 Related US. Application Data [63] Continuation of Ser. .No.121,164, March 4, 1971, I

abandoned.

[30] Foreign Application Priority Data- Mar. 4, 1970 Switzerland 3133/70Jan. 15, 1971 Switzerland 625/71 [52] US. Cl. 8/12; 8/l2.5; 8/13 [51]Int. CI. D06P 3/32; D06P 5/QO; D06P 3/12;

[58] Field of Search 8/12, 12.5, 13

[56] References Cited I UNITED STATES PATENTS 9/1956 Meyer et al 8/123,414,366 12/1968 Nordstrom et al 8/12 3,472,605 10/1969 Wicki et a1.8/12 FOREIGN PATENTS OR APPLICATIONS 1,069,574 5/1967 United Kingdom8/12 737,865 2/1970 Belgium 8/12 Primary Examiner-Benjamin R. PadgettAssistant Examiner-T. S. Gron Attorney, Agent, or F irmJoseph G.Kolodny; Edward McC. Roberts; Prabodh l. Almaula [57] ABSTRACTexpressing the dyeing liquor from the dyed leather, and subsequentlydrying the leather or subjecting the leather to a fixing process andthen drying it.

Compared to the known method of dyeing leather in the vat, that is tosay in a closed rotating drum in which the leather material is exposedto severe mechanical stress for a prolonged period, for example for 1hour, the process of the present invention offers considerableadvantages. The process of the invention treats the materials verygently: because of the short dyeing time, the stage of washing orrinsing the dyed goods is dispensed with, and furthermore the processcan be carried out continuously, so that the material throughput can beconsiderably increased and the auxiliaries and apparatus required forthe process are less expensive.

Compared to the process described in German Pat. Nos. 1,226,529 and1,287,556, the present process has the advantage of greater simplicitysince, according to the present process, dyeing is no longer carried outin a complicated aqueous two-phase system, but in a singlephase solventsystem which is simple to manufacture. The presence of one or moreorganic solvents in the dyeing solution renders the dyestuffs moresoluble, leads to better, that is to say more rapid, wettability of theleather to be dyed and effects a rapid and deep penetration of thedyestuff into the leather. The shortening of the dyeing time therebyachieved at the same time permits dyeing at a higher temperature, whichmakes the dyeing process even more effective. In the method of dyeing inthe vat, in particular, the use of high temperatures is not possiblesince, as a resultof the longer dyeing time and the mechanical stress,damage to the leather cannot be avoided at higher temperatures. For theprocesses described in the German specifications mentioned above, dyeingtemperatures of 50 solutions containing organic solvents.

An aqueousdyestuff solution that contains an organic, water-misciblesolvent is a preferred dyeing solution. Depending on the proportion ofthe organic solvent in the aqueous solution, the dyestuff or thesolution penetrates more or less rapidly and deeply into the leathermaterial. If the dyeing solution contains a sufficient amount of organicsolvent, the speed of penetration is so great that very short dyeingtimes, for example 5 to seconds, suffice. If additionally the tempera--ture of the dyeing solution is raised, dyeing times of up to 5 secondsmay suffice to achieve a good colour intensity. As examples ofwater-miscible organic solvents that are suitable for use as an additiveto the aqueous dyestuff solutions,there may be mentioned: methanol,ethanol, propanol, butanol, ethylglycol, methoxyethyl alcohol, glycerol,acetone, dimethylformamide, tetrahydrofurane, and especiallyisopropanol.

If a wetting agent and dispersing agent is added to the aqueous dyeingsolution, the amount of the organic solventcan be reduced, or theorganic solvent can be omitted entirely, without having to lengthen thedyeing times. Suitable wetting agents and dispersing agents are, forexample, reaction products of higher-molecular fatty acids withhydroxyalkylamines and, optionally, ethylene oxide.

If a dyeing solution that only contains one or more organic solvents isused for the process according to the invention, it is of coursenecessary to use a solvent or solvent mixture that is capable ofdissolving the dyestuff concerned, for example acetone foracetone-soluble dyestuffs. Depending on the nature of the dyestuffsused, entirely different solvents will thus be employed,

for example ethanol, ether, petrol, benzene, chloroform, carbondisulfide turpentine oil, carbon tetrachloride, trichloroethylene, ethylacetate or butyl acetate. However, pigment dyestuffs that are used in adispersed form in. suitable solvents, for example those mentioned above,or in liquid lacquers, that contain, for example,

linseed oil, turpentine oil, ethanol, benzene, butyl acetate, amylacetate, ether, acetone or petrol as solvents,

can also be used for the process according to the invention.

Possible dyestuffs are all those that are suitable for dyeing leather,-for example, reactive dyestuffs, acid wool dyestuffs, liquid cationicdyestuffs and especially metal complex dyestuffs. As trade names of suchdyestuffs, there may be mentioned Cibalene, Lanasol, Cibacron, Procionand Levafix dyestuffs.

It is important that the dyestuff should be used in a concentrated formwhich is as pure as possible, that is to say it should contain as littleas possible in the way of diluents (cutting agents or extenders), forexample inorganic salts, such as sodium sulphate, sodium chloride ordextrins, or 'wetting agents and dispersing agents, since the leather isno longer washed or rinsed after dyeing, and the cutting agents orextenders are hence no longer removed.

After removing the dyed leather from the bath, the excess dyeing liquoris expressed from it as thoroughly as possible. Thereafter, the dyedmaterial is further processed in the usual manner by drying it, orfixing and drying it. The fixing can be carried out in a manner knownper se, for example, by the cold padbatch method in the case of reactivedyestuffs. Drying is also carried out in a manner known per se, forexample in an infra-red drying oven or vacuum drier. In some cases it isadvantageous if the dyed material is stored for some time, for examplefor l to 24 hours, after expressing the dyeing solution and beforefurther processing. Possible leathers that may be dyed are all varietiesof leather, and especially chrome leather.

Because of the very short dyeing times that are possible, as alreadymentioned, the process according to the invention can also be carriedout continuously, so that the processes of immersing the leather intothe dyebath,,removing it, expressing it and treating it further arecarried out in a continuous process with a constant feeding-in ofmaterial. A suitable dyeing device is a trough containing the dyeingsolution, through which the leather material to be dyed is moved bymeans of a conveyor device, for example a conveyor belt. A suitableexpression device is a roll-padder into which the leather material isfed by the conveyor belt immediately after leaving the dyebath, and inwhich the bulk of the dyeing liquor retained in the dyed leather isexpressed. The subsequent drying, or fixing and drying, of the dyedmaterial is effected with the aid of devices known in dyeing technologythat can also run automatically. In this way, a piece of leather canpass within a few minutes through the entire processing sequence in thecombined dyeing-padderdrying arrangement. If dyeing solutions are usedthat only contain organic solvents, it is advisable to carry out theprocess according to the invention in a closed device, in order to avoidobjectionable odours or hazards from solvent vapours. Furthermore, it ishighly advantageous that the solvent vapours produced when drying thedyed leather should be condensed, in order to recover the solvents.

In the following Examples the parts, unless otherwise stated, are partsby weight, and the percentages are percentages by weight.

EXAMPLE 1 A dyestuff solution is prepared by dissolving 10 parts of themixed chromium complex dyestuff which contains one molecule of thedyestuff of the formula and one molecule of the dyestuff of the formulaHO CH5 H on N=N O bonded as a complex to one atom of chromium, in 785parts of water, 200 parts of isopropyl alcohol and 5 parts of 85strength formic acid.

Buffed side leather which has been chrome and vegetable re-tanned iscontinuously impregnated in a trough containing the dyestuff solutiondescribed above, using a dwell time of seconds at a temperature of 60C,taken out of the trough and expressed between two squeeze rollers, to adyestuff solution uptake of about 80 of its weight, and dried in avacuum drier. Brown shades that are level in colour and uniform incolour shade are thus obtained.

EXAMPLE 2 Chrome-tanned suede leather can be dyed red in the 4 mannerdescribed in Example 1 if the following solution is used with a dwelltime of 8 seconds, a temperature of C and 70 solution uptake: a dyestuffsolution of l2.-parts of the 1:2 chromium complex of the dyestuff of theformula HQ 0 H OH 3 c rr N=N -c l l N 0 s 1 936 parts of water, 50 partsof isopropanol/ethylglycol (1:1) and 20 parts of the product obtained asfollows:

420 g of technical oleic acid (1.5 mols), 345 g of diethanolamine (3.35mols) and 1.5 g of p-toluene-sulphonic acid are kept under nitrogen at160to 165C, in a 1 litre round-bottomed flask equipped with a stirrer,thermometer and descending condenser, until 27 to 28 ccs of water havecollected in the ice-cooled receiver. 740 g of the reaction product areobtained.

After drying the dyed leather by hanging up in a drying chamber at 50C,a level red dyeing is obtained.

EXAMPLE 3 .As in Example 1, but observing the following conditions:chrome and vegetable re-tanned full grain side leather, dwell time 6seconds at 65C and dyestuff solution uptake Dyestuff solution of 12parts of the dyestuff of the formula 10 parts of 85% strength formicacid, 878 parts of water and parts of isopropanol/ethanol (1:1). Dryingon a vacuum drier.

, EXAMPLE 4 As in Example 1, but observing the following conditions:chrome-tanned nubuk leather, dwell time 5 seconds at 70C and dyestuffsolution uptake 80%. Dyestuff solution of 15 parts of the dyestuff ofthe formula obtained.

' and one molecule of the dyestuff of the formula 30 parts of thereaction product of'oleic acid and-diethanolamine describedin" Example2,5755 parts of water and 200 parts of isopropanol; subsequent fixing ina padder at 50" c using a mixture of 30 partsof-a'dicyandiamide-fonnaldehyde condensation T product, 10 parts of 85%strength formic acid and 960 parts of water, and drying on a stretchingfr'ameyRed dyeings are OH HO I HIl (JO-CH bonded as a complex to oneatom of chromium is used and topping is carried out on a padder with 5parts of a mixture of 20 parts of Methylene Blue, 34 parts of BismarckBrown, and 46 parts of Meldolas Blue (Cl.

I Basic Blue 6), 20 parts of 80% strength acetic acid, 875 parts ofwater and 100 parts of ethanol. Black shades are obtained.

EXAMPLE 6 stuff from B-naphthylamine and diazotised 5-nitro-2-aminophenol, 200 parts of ethyl acetate, 500 parts of 6 ethylglycol, 240parts of isopropyl alcohol, 40 parts of -vinyl copolymer and 10 parts ofacrylate polymer. Subsequent drying. Black shades are thus obtained.

EXAMPLE 7 parts of the 1:2 cobalt mixed complex dyestuff which containsone molecule of the azo compound of the formula Cl NH and one moleculeof the azo compound of the formula 0H HO bonded to one atom of cobalt,and 10 parts of a levelling agent, are dissolved in 970 parts of water.

Chrome-tanned and synthetics-vegetable retanned side leather isimpregnated, for a dwell time of 12 seconds and at a temperature of 70C,in a trough which contains the dyeing solution described above, and isexpressed to a 70 liquor uptake and dried in a vacuum drier. A levelclaret-coloured leather is obtained.

EXAMPLE 8 A dyestuff solution is prepared from 20 parts of the 1:1cobalt complex dyestuff of the monoazo compound obtained by couplingdiazotised 2-amino-4-nitrophenol with acetoacetanilide, 10 parts of alevelling agent, 100 parts of ethylglycol and 870 parts of water.

Chrome-synthetics-tanned side leather is dyed in this solution, asdescribed in Example 1, using a dwell time of 10 seconds in a bath at C.The leather is then expressed to a liquor uptake and is dried in avacuum drier at C. A yellow-coloured leather is obtained.

We claim:

1. In a process for dyeing leather by a single treatment of the leatherwith a dye liquor which is an organic-solvent solution of a dyestuff,expressing the liquor from the dyed leather immediately upon leaving thedye liquor, optionally fixing the dyestuff, and finally drying the dyedleather without prior washing, the improvement which consistsessentially of continuously treating the leather, in the substantialabsence of mechanical stress, at a temperature of 25 to 80C, for aperiod of up to 15 seconds, with a liquor of a dyestuff dissolved in acombination of water and a watermiscible organic solvent selected fromthe group consisting of lower alkanol having 1 to 4 carbon atoms,ethylglycol, methoxyethyl alcohol, glycerol, acetone and tetahydrofuran.

2. The process of claim 1, wherein the watermiscible organic solvent isisopropyl alcohol. 3. The process of claim 1, wherein the liquor furthercontains a surfactant selected from the group consist- 65 ing of areaction product of a higher molecular fatty acid with hydroxyalkylamineand a reaction product of higher molecular fatty acid withhydroxyalkylamine and ethylene oxide.

4. The process of claim 1, wherein the dyestuff is a metal complex,reactive, or cationic dyestuff.

5. The process of claim 1, wherein the treatment is carried out for aperiod of to 10 seconds.

6. The process of claim 1, wherein the treatment is carried out at atemperature in the range of 60 to 80C.

7. The process of claim 1, wherein the dyed leather is stored for aperiod of l to 24 hours after the step of expressing the dye liquor, andbefore drying the leather.

8. The process of claim 1, wherein the leather is chrome-tanned leather.

9. In a process for dyeing leather by a single treatment of the leatherwith a dye liquor which is an organic-solvent solution of a dyestuff,expressing the liquor 10. The process of claim 9, wherein the treatmenttime is 5 to 10 seconds, and the treatment is carried out at atemperature in the range of to C.

1. IN A PROCESS FOR DYEING LEATHER BY A SINGLE TREATMENT OF THE LEATHERWITH A DYE LIQUOR WHICH IS AN ORGANIC-SOLVENT SOLUTION OF A DYESTUFF,EXPRESSING THE LIQUOR FROM THE DYED LEATHER IMMEDIATELY UPON LEAVING THELIQUOR, OPTIONALLY FIXING THE DYESTUFF, AND FINALLY DRYING THE DYEDLEATHER WITHOUT PRIOR WASHING, THE IMPROVEMENT WHICH CONSISTSESSENTIALLY OF CONTINUOUSLY TREATING THE LEATHER, IN THE SUBSTANTIALABSENCE OF MECHANICAL STRESS, AT A TEMPERATURE OF 25* TO 80*C, FOR APERIOD OF UP TO 15 SECONDS, WITH A LIQUOR OF A DYESTUFF DISSOLVED IN ACOMBINATION OF WATER AND A WATER MISICIBLE ORGANIC SOLVENT SELECTED FROMTHE GROUP CONSISTING OF LOWER ALKANOL HAVING 1 TO 4 CARBON ATOMS,ETHYLGLYCOL, METHOXYETHYL ALCOHOL, GLYCEROL, ACETONE ANDTETRAHYDROFURAN.
 2. The process of claim 1, wherein the watermiscibleorganic solvent is isopropyl alcohol.
 3. The process of claim 1, whereinthe liquor further contains a surfactant selected from the groupconsisting of a reaction product of a higher molecular fatty acid withhydroxyalkylamine and a reaction product of higher molecular fatty acidwith hydroxyalkylamine and ethylene oxide.
 4. The process of claim 1,wherein the dyestuff is a metal complex, reactive, or cationic dyestuff.5. The process of claim 1, wherein the treatment is carried out for aperiod of 5 to 10 seconds.
 6. The process of claim 1, wherein thetreatment is carried out at a temperature in the range of 60* to 80*C.7. The process of claim 1, wherein the dyed leather is stored for aperiod of 1 to 24 hours after the step of expressing the dye liquor, andbefore drying the leather.
 8. The process of claim 1, wherein theleather is chrome-tanned leather.
 9. IN A PROCESS FOR DYEING LEATHER BYA SINGLE TREATMENT OF THE LEATHER WITH A DYE LIQUOR WHICH IS ANOARGNIC-SOLVENT SOLUTION OF A DYESTUFF, EXPRESSING THE LIQUOR FROM THEDYED LEATHER IMMEDIATELY UPON LEAVING THE DYE LIQUOR, OPTIONALLY FIXINGTHE DYESTUFF, AND FINALLY DRYING THE DYED LEATHER WITHOUT PRIOR WASHING,THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF CONTINUOUSLY TREATING THELEATHER, IN THE SUBSTANTIAL ABSENCE OF MECHANICAL STRESS, AT ATEMPERATURE OF 25* TO 80*C, FOR A PERIOD OF UP TO 15 SECONDS, WITH ALIQUOR OF DYESTUFF DISSOLVED O IN AN ORGANIC SOLVENT SELECTED FROM THEGROUP CONSISTING OF ACETONE, ETHANOL, ETHER, PETROL, BENZENE,CHLOROFORM, CARBON DISULPHIDE, TURPENTINE OIL, CARBON TETRACHLORIDE,TRICHLOROETHYLENE, ETHYL ACETATE AND BUTYL ACETATE.
 10. The process ofclaim 9, wherein the treatment time is 5 to 10 seconds, and thetreatment is carried out at a temperature in the range of 60* to 80*C.